Not Applicable
1. Field of the Invention
This invention relates to a medical instrument for filling a cavity formed within bone, a spinal disk, or a fixation device inserted therein, with biocompatible beads. More specifically, the present invention is directed to a vibratory tool having a reservoir of biocompatible material in fluid communication with a proximal end of a tubular injection cylinder, the injection cylinder and reservoir are vibrated to cause the material to pass from the reservoir into the proximal end of the injection cylinder. The vibratory action of the device and gravity allow the material to pass through the injection cylinder to its distal end and be deposited into a delivery site. The vibratory action of the injection cylinder causes the distal end of the cylinder to gently tap the deposited material thereby compacting the material within the delivery site. The unique construction and vibratory action of the present device prevents fill material from plugging the device during use and provides for a consistent flow of fill material into the delivery site.
2. Description of the Related Art
Bioceramic compounds and other types of fill material such as bone may be used as a fill material in the treatment of certain orthopaedic conditions; including fractures, non-unions, tumors, and cysts and as an adjunct to certain fusion procedures. In general, these conditions involve filling a cavity that has been created by the pathology itself or by the action of the surgeon during removal of the pathology.
The cavity may be filled by the placement of a block of fill material or by the gradual addition of granules of fill material such as bioceramic beads, crushed bone or a combination thereof. Alternatively, a variety of different types of support and/or joining devices may be inserted into the cavity. These devices may be filled with the fill or graft material, as opposed to directly filing the cavity therewith.
Devices such as those used in spinal fixation are well known in the art. Such devices may include apparatuses which are inserted into hollowed out portions of a spinal disk or vertebrae. For example, U.S. Pat. No. 5,549,679 issued Aug. 20, 1996 and U.S. Pat. No. 5,571,189 which issued Nov. 5, 1996, both of which being incorporated in their entirety herein by reference, disclose an expandable fabric bag and method for stabilizing a spinal motion segment. In these patents, a damaged disc is reamed out and an expandable fabric bag is inserted into the cavity thus formed. Bone graft material is then inserted into the bag to fill and expand the bag such that the filled bag will take the place of the reamed out disc. Over time, the material within the bag will cause a fusion of the adjacent vertebrae. The bag filling is through an opening which is closed off after filling.
Another device and method for stabilizing a spinal motion segment is described in co-pending U.S. Provisional App. No. 60/256,014 filed Dec. 15, 2000, the entire contents of which being incorporated herein by reference. In this Application a band of fabric or mesh is inserted into a reamed out cavity within a disk or other spinal body. The fabric of the band may be structured to allow a bone graft fill tool to penetrate the band, without causing it damage, and deposit fill material into the area defined by the band and surrounding tissue.
These and other devices are intended to provide support to the spinal segment which they are being inserted into and to encourage fusion of the surrounding spinal bodies through the device. A key aspect to such devices is the proper placement and compaction of bone graft material into the site through which bone growth and eventual fusion is to take place.
As indicated above the cavity or device may be filled with material in a variety of different manners. Manual filling such as by insertion by hand of one or more chunks of fill material may not provide for ideal filling and compaction characteristics which may be essential to encouraging proper bone growth and fusion. The use of granular material in gradually filling the cavity, or a device inserted therein has the advantage of allowing filling through a smaller entrance portal. In addition, by gradually filling the cavity or device with granular fill material allows the cavity to be filled in a more uniform and complete manner.
In use however, granular material such as ceramic granules tend to jam within injection tubes and tend to break apart and pulverize when injection and/or impaction forces are vigorously applied. Broken or pulverized granules of bioceramic compounds contain fine dust particles that have been shown to inhibit bone growth.
The granules may exist in a variety of shapes and sizes, such as, for example amorphous chunks or solid geometric shapes. Of the various available granule shapes, spherical shaped beads provide several potential advantages over other granular shapes. Notably, spherical beads may provide maximal and consistent inter-granule porosity and improved flowability. However, even spherical granules are known to jam and break apart during the injection procedure. Therefore, there is a need for a new method of granule injection that is easier, faster, and produces less jamming and granule breakage.
Experiments have been conducted with various means to more efficiently and effectively introduce granular material into cavities. The goal of these experiments was to develop a novel means for improving spherical granule flow while minimizing the breakage of granules. As a result of these experiments the device of the present invention was constructed. The present device was determined to provide the best combination of flow efficiency and the least tendency toward granule breakage during the fill process. By utilizing the present invention for inserting bioceramic beads or other fill material into a body cavity, the invention may improve the care of patients with certain orthopaedic conditions.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is xe2x80x9cprior artxe2x80x9d with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. xc2xa71.56(a) exists.
The entire content of all of the patents listed within the present patent application are incorporated herein by reference.
In light of the above, the present invention is directed to a method and apparatus which provides for improved filling and compaction of bone graft material within a hollowed portion of a bone, spinal segment or a fixation device positioned therein.
In at least one embodiment, the present invention is directed to a filling instrument that directs one granule or bead to drop into a tube from a bead reservoir, upon dropping a bead into the tube, the tube and reservoir are pneumatically actuated to pop back up to unblock the granules therein, which in turn allows another bead or granule to drop into the tube in repeating cycles. The present device agitates the granules at each stroke so they fill up the tube. The up and down motion of the tube and reservoir also provides for compaction of the beads at the distal end of the tube which may compact the beads into the chamber or spinal fixation device being filled.
The present invention allows the surgeon to fill body cavities more easily and completely, with less damage to granules, and through a very small entrance portal. The invention also provides a means to compact the granular mass, thereby improving the fill density and the stability of the granular pack.
The invention provides for a bead reservoir that is submitted to vibratory energy that encourages the bead pack to flow into a hollow, tubular injection cylinder. Pneumatic, hydraulic, or other mechanical forces then cause the injection cylinder to oscillate along its longitudinal axis, while the beads are gently pushed into the cavity by a combination of frictional forces against the cylinder walls and the pull of gravity.
Once the cavity is filled or nearly filled, the distal tip of the oscillating cavity gently taps the top of the bead pack, thereby forcing the beads into a more densely packed construct.
As indicated above, one application of the invention is in the field of spinal surgery. Surgeons often attempt to fill certain spaces within the spine with bone or bone substitute materials, such as bioceramic material. The filled spaces then provide mechanical support and the proper milieu for bone ingrowth. The local spinal anatomy restricts safe access to certain internal spinal areas. Therefore, surgeons are often required to operate through very small entry portals. The present invention provides the surgeon with a reliable and effective device suitable for filling cavities deep within the spine, e.g. the interbody or intra-vertebral spaces.
One particularly common spinal procedure is known as an interbody fusion. In the interbody fusion procedure, the surgeon attempts to fill the gap between two opposing vertebrae with a material and/or device that supports load and encourages bony ingrowth. Such devices include, but are not limited to, those described in U.S. Pat. Nos. 5,489,308; 5,549,679; 5,571,189 and others.
As shall be made clear from the description below, in at least one embodiment of the invention, the present device may be inserted through very small diameter tubes. As a result, it is possible to fill the intervertebral space with little or no retraction of sensitive local nerves and vessels. For example, this invention allows the surgeon to fill the interbody space through a portal substantially smaller than currently required for many procedures.
Another area where the present invention may be of use would be in procedures known as vertebra-plasties or kypho-plasties, wherein the surgeon attempts to fill the area occupied by a so-called xe2x80x9ccompression fracturexe2x80x9d of the vertebral body. The present invention could be used to fill this area through the narrow confines of the vertebral pedicle or through a small (about 3-10 mm) hole in the side or front of the vertebral body. As a result, use of the invention would reasonably reduce risk and complications compared to other procedures that require a larger exposure, as in the case of the placement of large bioceramic blocks.